1. Technical Field of the Invention
This invention relates generally to suspension components for two-wheeled vehicles, and more specifically to front steering and front spring/shock components.
2. Background Art
The vast majority of motorcycles (and full- and front-suspension bicycles) are equipped with front suspensions in which a pair of telescopic forks are coupled to the steering head of the motorcycle's frame by an upper triple clamp and a lower triple clamp. The triple clamps provide enough lateral offset that the forks clear the sides of the front tire. The triple clamps are usually constructed to provide some measure of longitudinal offset, as well, to increase trail and thereby stabilize the motorcycle. Trail is a measurement, on the ground, from a point projected through steering axis to the center of the tire's contact patch directly below the axle, and determines the self-centering stability of the steering. The forks are either of the “right-side-up” or sliding-female configuration, or the “upside-down” or sliding-male configuration. In either case, a cylindrical tube or piston slides axially within a cylindrical cylinder.
In nearly all cases, both the suspension springs and the damping or shock absorbing components are disposed within one or both of the sliding tube assemblies. Unfortunately, because the substantial mass of the springs, dampers, oil, and other related suspension components is located a significant distance—generally in the neighborhood of 2.5 inches—from the axis of the steering head, the front end has an undesirably large moment of rotational inertia. In other words, the front end has a heavy “swing weight” which reduces both the “feel” and the responsiveness of the front end.
Alternative front end configurations have occasionally been seen, but all suffer from this same malady, and their inventors have been attempting to solve other problems, such as front end “dive” under hard braking, rather than reducing the moment of rotational inertia. Examples include the well-known BMW Telelever, the Britten front end, the Hossack front end, the RADD-Yamaha front end, and various hub-center systems such as that found on the Bimota Tesi.
None of these previous geometries places the spring or damper components coaxial to the steering head, and all suffer from having stylistic, aesthetic appearances which are dramatically different than the almost universally preferred conventional dual fork system. Furthermore, all are significantly more complex than the conventional dual fork system. The downside of these previous systems, such as increased mass, outweigh any benefit they may have offered on other fronts.
Fork flex, especially under braking, is a significant contributor to the stiction which is known to dramatically reduce the effectiveness and perceived quality of a motorcycle's front suspension.
What is needed, then, is a system which has the aesthetic appeal and simplicity of the dual fork geometry, with a significantly reduced moment of rotational inertia. What is further needed is a system which offers reduced stiction.